Colloidal Nanocrystal Clusters Research Articles

Sequential assembly enhanced selectivity on magnetic imprinted polymers for specific capture of naringin: A combination of synergistic dual sites and imprinted effect

Green and sustainable recovery of high-value natural flavonoids in agricultural wastes could not only improve natural resource utilization, but also could effectively reduce environmental pollution. Recently, great efforts have been made for research on the development of magnetic imprinted composite adsorbent, but the simultaneous promotion of stable selectivity and high adsorption amounts still faces its challenges. Inspired by “Sandwich-like” transport channels with proper steric and specific affinity sites, herein we designed a new kind of surface-imprinted magnetic colloidal nanocrystal clusters (MCNCs) with dual recognition sites (MCNCs@DR-MIPs) via sequential surface imprinted strategy. A two-step sequential surface-initiated atom transfer radical polymerization (SI-ATRP) was employed to construct the double imprinted sites, which can significantly improve the adsorption selectivity and adsorption amounts. In this design, the metal ion Zn(II) and the low pKa boronic acid APBA (1-allylpyridine-3-boronic acid, pKa = 7.4) could effectively tune the appropriate yolk-shell confinement sites, the obtained artificial double imprinted binding sites establishes the promising chemical environment for selective separation. As expected, the adsorption equilibrium experiments exhibited adsorption kinetics (180 min) and the maximum equilibrium binding capacity (34.60 µmol g−1). In virtue of unique advantages of magnetic separation materials, this novel absorbent exhibited a green and environmentally friendly enrichment process for naringin (NRG). Meanwhile, MCNCs@DR-MIPs showed excellent selectivity (imprinted factor 2.15) and regeneration properties (only decreased by 8.22 % after 7 cycles) for NRG. Additionally, the commercially available NRG could be effectively extracted and concentrated to 94.78 %. This study offers a sustainable effective strategy for flavonoids purification of magnetic separation materials and promotes advance the other natural compounds from agricultural wastes.

Preparation of silicon quantum dots@star like bloc-copolymer (SiQD@S-BP) colloidal nanoclusters through in-situ reduction and confined growth

Here in this work, colloidal nanocrystal clusters (CNCs) formed by silicon quantum dots and star-like block-copolymers (SiQDs@S-BP) were prepared through in-situ reduction and confined growth method. Water-soluble star-like block copolymer β-CD-g-PAA-b-POEGA (unimolecular micelle) was precisely synthesized through ATRP and used as the templates for SiQDs@S-BP. Owing to the electrostatic interaction, the amino groups functionalized silicon can be adsorbed to the carboxyl groups in the polymer chains. After in-situ reduction and confined growth, silicon quantum dots were formed and monodispersed in the unimolecular micelles. Benefitting from the CNCs structure, the fluorescence emission of the SiQDs enhanced due to the aggregation induced emission enhancement (AIEE) effect. The inner structure and outer polymer brushes of the CNCs avoided the coalescence of SiQDs during application and collection, and made it more efficient in recycling and reusing.

Bifunctional hybrid magnetic colloidal clusters for efficient oil sludge recovery

Oil contamination of water bodies due to oil spills, industrial waste discharge, oil leaks, etc. poses a major threat to the quality of groundwater, soil, and living organisms. To combat this issue through effective environmental remediation, efficient and cost-effective materials and innovative strategies are required. Here, we report a novel bifunctional magnetic material for efficient oil sludge removal using superparamagnetic colloidal nanocrystal clusters(BSPM-CNC) of nickel ion doped iron oxide with a shell of nitrogen-activated carboxymethyl cellulose char. The BSPM-CNC is synthesized by using a single-step procedure using water as a solvent. The crystallite and cluster size were tuned by varying Ni2+ ion concentration, carboxymethyl cellulose, and urea ratio. The cluster size was found to increase, when the carboxymethyl cellulose and urea ratio was reduced, due to insufficient stabilization of the capping agent that allowed the formation of secondary structures. X-ray photoelectron spectroscopy results confirmed the presence of nitrogen in the shell because of the condensation of OH and carbonyl groups of CMC with amine groups of urea, sp2-type carbon, C-O/N and O-CO bonding states. Laser Raman spectra of the char showed two major bands G and D bands, originating from the sp2 bonds and sp2 microdomains of the bond angle disorder caused by the sp3 hybridizations, respectively. The BSPM-CNC was found to be very efficient for oil sludge removal, where an oil removal efficiency of ∼ 98% was achieved with a cluster loading of 16 mg/L. The mechanism of sorption of oil are π-π interaction between aromatic hydrocarbons and graphitic domains of BSPM-CNC, Lewis-acid base interaction between nitrogenous char and delocalized electron cloud, and absorption into the pores of clusters. Our new approach provides a new platform to produce magnetic nanoclusters for the efficient removal of oil pollutants.

Preparation of Lignosulfonate@AgNPs Colloidal Nanocrystal Clusters through In Situ Reduction, Confined Growth, and Self-Assembly

Preparation of Lignosulfonate@AgNPs Colloidal Nanocrystal Clusters through In Situ Reduction, Confined Growth, and Self-Assembly

Separation and purification of target flavonoids using covalently connected MOFs@boronic acid-functionalized-COFs magnetic hybrids: Precise identification and enhanced stability

The magnetic boronate based sorbents have been widely used to separation of cis-diol containing flavonoids. However, It's still challenging due to its chemical structural fragility and low grafting efficiency. The major obstacles are low concentration, the hydrophobicity of flavoniods, and complexity of crude extract solutions. For solving these problems, a new kind of covalently connect MOF@boronic acid-functionalized-COFs core–shell hybrid composites based on magnetic colloidal nanocrystal clusters (MCNCs), MCNCs@NH2-UiO-66@BTCA-BA-COFs, with high surface area, abundant binding sites and excellent chemical and structurally stability were synthesized for enhancing the structure stability and selective recognition efficiency. The alkynylation COFs were not only to be facilely grated on the surface of magnetic microsphere@NH2-UiO-66 via Schiff-based reaction but also beneficial to the further modification of azide phenylboronic acid group via click reaction. Such mentioned advantages and covalently connect click strategy could generate highly structure stable and strong binding sites for the template flavonoids (Naringin, NRG). Adsorption equilibrium experiments were reached rapidly within 120 min, and the maximum equilibrium binding capacities of MCNCs@PDA@NH2-UiO-66@BTCA-BA-COFs were 31.20 µmol g−1 for NRG. Moreover, MCNCs@PDA@NH2-UiO-66@BTCA-BA-COFs exhibited a stronger selectivity towards NRG than other competitive targets (i.e rutin, catechol, hesperetin, o-nitrophenol). The MCNCs@PDA@NH2-UiO-66@BTCA-BA-COFs have shown outstanding reusability of 91.99 % loss in enrichment performance towards NRG after seven times repeatedly. The obtained MCNCs@PDA@NH2-UiO-66@BTCA-BA-COFs-based mass spectrum (MS) methods were applied to analyze the purity of NRG products. As excepted, a commercially available NRG with purity (approximately 60 %) could be effectively extracted and concentrated to 93.15 % purity. More interestingly, the separation performance of the sorbents was influenced by hydrophilic and hydrophobic performance. This approach provided an idea for constructing a new kind of hybrid sorbents with both enhanced functionality, suitable hydrophobic performance and fast magnetic-response behavior, which is of great significance to the field of separation and purification of hydrophobic flavonoids.

Polyphenol‐Mediated Synthesis of Superparamagnetic Magnetite Nanoclusters for Highly Stable Magnetically Responsive Photonic Crystals

AbstractAchieving high stability and excellent optical performance in complex environments is crucial for practical applications of magnetically responsive photonic crystals (MRPCs). It, however, remains a great challenge. This study demonstrates a polyphenol‐mediated strategy for synthesizing size‐controllable superparamagnetic magnetite (Fe3O4) colloid nanocrystal clusters (CNCs) that can be stably dispersed in various polar solvents to form MRPCs with brilliant structural colors for a long term. As tannic acid (TA) functions as a linker to robustly bind polyvinylpyrrolidone (PVP) chains to Fe3O4 surfaces, the MRPCs can maintain nearly constant diffraction wavelength and high reflectance for up to 4 years. The strong coordination between TA and Fe3+ inhibits crystal growth, ensuring the small primary crystal size and superparamagnetism of Fe3O4@TA‐PVP CNCs. Partial oxidation of TA accelerates the crystal nucleation and growth, reducing the overall CNC particle size, which can be utilized for controlling the particle size. Additionally, enhancing the dissolution of PVP before the solvothermal reaction improves the size monodispersity of the products, making the as‐constructed MRPCs ideal for practical applications in color display, sensors, anti‐counterfeiting, and camouflage. The Fe3O4@TA‐PVP CNCs with high stability and versatility for surface‐functionalization are also promising for magnetic resonance imaging, targeting drug delivery, recyclable catalysis, and magnetic nanomotors.

Grain boundary and lattice distortion enriched platinum-nickel/ceria colloidal nanoparticle clusters for highly efficient electrooxidation of liquid fuels

Clustering pony-size nanocrystals into secondary structures (colloidal nanocrystal clusters, CNCs) not only combines the properties of primary nanocrystals, but also obtains the novel functions originated from the strengthened interactions between neighboring nanocrystals. Herein, we use the PtNi clusters and CeO2 clusters as the primary subunits to construct the PtNi/CeO2 CNCs, which can enhance the interaction between PtNi and CeO2 clusters, as well as improve the electron conductivity of CeO2 originated from the strengthened attachment. Plenty of grain boundaries and lattice distortion generated after introducing the CeO2 clusters into the inner surface of PtNi CNCs, which improves the electrooxidation activity and anti-CO-poisoning ability of PtNi/CeO2 CNCs. Specifically, the PtNi/CeO2 CNCs exhibited higher specific activities than PtNi CNCs towards electrooxidation reactions of methanol, formic acid and ethylene glycol, as well as 8.5, 7.7 and 7.0 times higher than those of Pt/C, respectively, along with enhanced stability. Combined with the experiments and characterizations, the improved property is originated from the novel functions of grain boundary, subtle lattice distortion and strengthened interaction. This study realizes architectural engineering of CNCs with quite different nanocrystal subunits, and creates an effective strategy for eliminating the disadvantages of conventional Pt/CeO2 catalyst in electrooxidation of liquid fuels.

Preliminary Evaluation of Iron Oxide Nanoparticles Radiolabeled with 68Ga and 177Lu as Potential Theranostic Agents

Theranostic radioisotope pairs such as Gallium-68 (68Ga) for Positron Emission Tomography (PET) and Lutetium-177 (177Lu) for radioisotopic therapy, in conjunction with nanoparticles (NPs), are an emerging field in the treatment of cancer. The present work aims to demonstrate the ability of condensed colloidal nanocrystal clusters (co-CNCs) comprised of iron oxide nanoparticles, coated with alginic acid (MA) and stabilized by a layer of polyethylene glycol (MAPEG) to be directly radiolabeled with 68Ga and its therapeutic analog 177Lu. 68Ga/177Lu- MA and MAPEG were investigated for their in vitro stability. The biocompatibility of the non-radiolabeled nanoparticles, as well as the cytotoxicity of MA, MAPEG, and [177Lu]Lu-MAPEG were assessed on 4T1 cells. Finally, the ex vivo biodistribution of the 68Ga-labeled NPs as well as [177Lu]Lu-MAPEG was investigated in normal mice. Radiolabeling with both radioisotopes took place via a simple and direct labelling method without further purification. Hemocompatibility was verified for both NPs, while MTT studies demonstrated the non-cytotoxic profile of the nanocarriers and the dose-dependent toxicity for [177Lu]Lu-MAPEG. The radiolabeled nanoparticles mainly accumulated in RES organs. Based on our preliminary results, we conclude that MAPEG could be further investigated as a theranostic agent for PET diagnosis and therapy of cancer.

Synthesis of Ni doped iron oxide colloidal nanocrystal clusters using poly(N-isopropylacrylamide) templates for efficient recovery of cefixime and methylene blue

The synthesis of a complex hierarchical nanostructure with a definite number density and crystallite/cluster size is very challenging. Here we report a novel strategy to produce spherical magnetic colloidal nanocrystal clusters (Ni-doped iron oxide) of varying sizes using a thermosensitive polymer soft template through a hydrothermal approach. The magnetic colloidal nanocrystal clusters are nucleated in the globular spherical templates formed in the thermosensitive polymer; poly(N-isopropyl acrylamide), above lower critical solution temperature (LCST) where it acts as a nucleating agent in the initial stage and as a capping agent later. When the solution reaches super-saturation during the nucleation stage, the Ni2+, Fe2+ and Fe3+ hydroxides precipitate as ferrites of critical size and get attached to the PNIPAM globule through the coordination of oxygen and nitrogen. It was observed that, after the addition of Ni2+ ions, non-stoichiometric Ni ferrites nanocrystals were formed whereas the hematite phase was formed in the absence of Ni doping. XPS results show the presence of cation vacancies due to oxidation of Ni2+ and Fe2+. We also studied the adsorption/desorption of an anionic cefixime drug, conjugated on nanoclusters, above and below the lower critical solution temperature. The cefixime adsorption studies on the clusters showed that ~70 g/L of the sample is required to obtain a 66 sorption% at 25 °C and 52 sorption% at 45 °C. The percentage of cefixime sorption after the five cycles of regeneration was ~70%. The dye adsorption studies reveal that 15 g/L of the sample showed 99% sorption% of methylene blue at 25 °C and 87% sorption% at 45 °C This approach can be used as a new strategy to achieve controlled recovery of adsorbates (antibiotics and dyes) from aqueous solutions.

A genosensor platform based on DNA biofunctionalized SNCNCs coupled with “IS-primer” amplification reaction for sensitive and rapid Listeria monocytogenes detection

Accurate and timely diagnosis of Listeria monocytogenes (L. monocytogenes), a well-known foodborne pathogen with a serious threat to human life and health, is critical for managing bacterial infections and food quality. Here, we report a genosensor platform based on DNA biofunctionalized superparamagnetic nickel colloidal nanocrystal clusters (SNCNCs) coupling with “IS-primer” amplification reaction (ISAR) for rapid, ultrasensitive and specific L. monocytogenes detection. Specifically, the catalytic activity of SNCNCs was identified. After three-step modification, the signal unit was formed by immobilizing AuNPs and hairpin probes on the surface of SNCNCs, achieving enhanced catalytic activity, leading to the reduction of a colorimetric substrate 4-nitrophenol (4-NP). The in-situ signal amplification of target RNA on the surface of SNCNCs coupling with ISAR showed high sensitivity and a detection limit of 1.50 × 10-3 ng mL-1 under optimized conditions. As SNCNCs can bind and lyse bacteria, this genosensor can detect live L. monocytogenes without RNA extraction, with a detection limit of 3.80 × 102 CFU mL-1. Furthermore, the system could also detect L. monocytogenes in artificially contaminated milk samples within 6 h. These results indicate the great potential of our method for sensitive, specific, convenient and low-cost bacterial detection in food, environment and clinics.

Facile preparation of lignosulfonate-based superparamagnetic colloidal nanocrystal clusters (CNCs)

Colloidal nanocrystal clusters (CNCs) are hierarchical nanostructure formed by clustering several nanocrystals into one nano-ensemble. In this work, novel lignosulfonate (LS)-based superparamagnetic CNCs were prepared for the first time. The strategy based on electrostatic interaction between LS, nanocrystals and charge control agent, and included multistep of surface modification, precipitation and self-assembly. With the protection of LS and blocking of CTAB, individual γ-Fe2O3 nanocrystals in the colloidal particles can keep monodisperse to form the cluster morphology. The superparamagnetic γ-Fe2O3 endowed superparamagnetic property to the CNCs, and the saturation magnetization value of CNCs increased with the increase number of nanocrystals in the LS spheres. Furthermore, the LS-based superparamagnetic CNCs showed excellent dye adsorption efficiency for different dyes, especially for positive charged cationic dyes.

General Route to Colloidal Nanocrystal Clusters with Precise Hierarchical Control via Star-like Nanoreactors.

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.

Magnetron traps therapeutics for localized bacterial capture and overcome ulcer infection

In addition to the pandemic caused by the coronavirus disease 2019, many pathogenic bacteria have also been posing a devastating threat to human health. The overuse of antibiotics leads to the emergence of ‘superbugs’; therefore, it is urgent to develop effective strategies to fight bacteria. Herein, a superparamagnetic nickel (Ni) colloidal nanocrystal clusters (SNCNCs) that can kill and capture bacteria without any camouflage is reported. It binds to amino groups on the surface of bacteria, imparts magnetism to them, and orients them in response to magnetic fields. SNCNCs kill and capture bacteria to avoid inflammation, infection, and organ damage caused by lipopolysaccharide and exotoxin released by bacterial rupture in the remaining bacterial remains in comparison with other antibacterial agents. In this study, in the treatment of traumatic oral ulcers, we found that SNCNCs could kill and capture and remove bacteria from the ulcers to reduce inflammation at the site of the wound. Furthermore, the fibrin gel sprayed on the ulcer was used as a substrate, and the bacteria captured by the SNCNCs moved to the surface of the fibrin gel after a magnetic field was applied. Therefore, the bacteria in the ulcer could be removed with the SNCNCs and fibrin gel magnet, alleviating inflammation caused by bacteria and promoting ulcer healing. This magnetically controlled method of directional movement of bacteria may provide an applicative perspective for the therapy of bacterial infections.

An Environmental Perception Self‐Adaptive Discolorable Hydrogel Film toward Sensing and Display

AbstractVision perception, especially color change, is the most direct and convenient way of feedback among numerous information recognition modes. Because of unique discoloration property upon stimulation, photonic crystals have attracted wide attention. Herein, with a facile UV polymerization process under the magnetic field, a sensitive photonic hydrogel film with vivid structural color is made. The structural color comes from the 1D chain‐like structures assembled by the carbon‐encapsulated Fe3O4 colloidal nanocrystal clusters (Fe3O4@CNCs), which are embedded in the flexible hydrogel matrix. The hydrogel can adapt its size to the environment, resulting in the regulation of intergranular distance and apparent color variation. Thus, a hydrogel film with humidity, ion concentration, and stress responsivity can be obtained, showing high sensitivity, stability, and full reversibility in a wide range of visible spectrum. It can be designed as a reusable display board or applied to colorimetric measurements similar to pH test paper. Innovatively, the hydrogel film is integrated as back reflectors to improve the efficiency of semitransparent polymer solar cells while protecting devices. This structural color hydrogel film makes it easier to recognize environmental dynamic changes and provide a wider application prospect in optics devices, sensing, display, and diagnostics.

Magnetically Assembled Photonic Crystal Gels with Wide Thermochromic Range and High Sensitivity.

Thermochromic poly(N-isopropyl acrylamide) (PNIPAM) photonic crystal gels based on 1D magnetically assembling colloidal nanocrystal clusters have attracted much attention due to its convenient preparation process, striking color response, and good mechanical strength. However, there remain challenges to broaden the thermochromic range and improve the sensitivity for their iridescent color display. Here, a PNIPAM photonic gel with wide thermochromic range and high sensitivity is prepared by using four-arm star poly(ethylene glycol) acrylamide (PEGAAm) as cross-linker at appropriately reduced magnetic field strength as well as cross-linker content. PEGAAm improves the homogeneity of the microstructure in PNIPAM photonic gel and thus maintains the structure colors at a wide temperature range from room temperature to 44°C. The reduced magnetic field strength of 70Gs and low cross-linker content (the molar ratio of monomer to cross-linker of 300:1) lead to a large initial lattice spacing of the photonic gel and thus wide diffraction wavelength migration of 194nm. This optimized PNIPAM gel exhibits vivid iridescent colors from orange-red to indigo blue as temperature increases from 20 to 44°C with satisfactory repeatability. Therefore, it may be an ideal candidate for temperature sensors and displays with utility and accuracy such as low-temperature burns.

Magnetic Hyperthermia in the 400–1,100 kHz Frequency Range Using MIONs of Condensed Colloidal Nanocrystal Clusters

In the current study, we explored the magnetic hyperthermia performance of condensed–clustered magnetic iron oxide nanoparticles (MIONs) in the range of 400 kHz to 1.1 MHz at low field amplitudes. The strong interparticle interactions, present in such systems, can influence the hyperthermia power produced by MIONs. Herein, the heat dependence, as an increasing function of frequency, with a fixed magnetic field strength of 3 mT is recorded, revealing a direct relationship between the two physical quantities and a high heating efficiency for the condensed–clustered MIONs. In particular, the specific loss power (SLP) (or specific absorption rate [SAR]) parameter, which is the ratio of the heat power in watts produced per nanoparticle mass in grams, is linear to a good degree to the oscillating frequency with a step of roughly 30 W/g per 100 kHz increase. In addition, all the measurements were within the safety limits proposed by Hergt and Dutz criterion of H f ≤ 5 × 109A/ms for clinical application of magnetic fluid hyperthermia (MFH). Finally, the measured data of temperature vs. time at each frequency were interpreted in terms of simple thermodynamic arguments, thus extracting useful thermodynamic parameters for the heat power generated by the condensed–clustered MIONs.

Highly Stable CsPbBr3 Colloidal Nanocrystal Clusters as Photocatalysts in Polar Solvents.

One of the main challenges of all-inorganic cesium lead halide (CsPbX3) perovskite nanocrystals (NCs) in photocatalysis is their poor stability in hostile environments such as polar solvents. Herein, we report highly stable CsPbBr3 colloidal nanocrystal clusters (CNCs) with uniform morphology and size prepared by using a PVP-assisted reprecipitation method. A possible formation process through a self-assembly avenue is proposed. These CsPbBr3 CNCs exhibit much enhanced resistance against a variety of polar solvents in comparison with CsPbBr3 NCs obtained from the commonly used hot-injection method. In addition, this method can be generalized to the synthesis of lead-free perovskites CNCs. The as-prepared CsPbBr3 CNCs display good reactivity and high durability in photocatalytic degradation of methylene blue in alcoholic systems. This work will shed some light on the stabilization of perovskite NCs in polar solvents and perovskite NC-based photocatalysts.

Robust synthesis of highly charged superparamagnetic Fe3O4 colloidal nanocrystal clusters for magnetically responsive photonic crystals

Herein, highly charged superparamagnetic Fe3O4 colloidal nanocrystal clusters with uniform and widely tunable sizes have been synthesized by a robust and easily scalable solvothermal method for magnetically responsive photonic crystals.

Implanting Atomic Dispersed Ru in PtNi Colloidal Nanocrystal Clusters for Efficient Catalytic Performance in Electro-oxidation of Liquid Fuels.

Although PtRu alloy nanocatalysts have been certified to possess excellent electrocatalytic performance and CO-poisoning tolerance toward formic acid and methanol electro-oxidation, the unaffordable usages of ruthenium (Ru) and platinum (Pt) have greatly limited their widespread adoption. Here, a facile one-pot method is reported for implanting atomic dispersed Ru in PtNi colloidal nanocrystal clusters with different Ru/Pt/Ni molar ratios, greatly reducing the dosages of Pt and Ru, and further improving the catalytic performances for the electro-oxidation of formic acid and methanol. Through simple control of the amount of Ni(acac)2 precursor, trimetallic Ru0.3 Pt70.5 Ni29.2 , Ru0.6 Pt55.9 Ni43.5 , Ru0.2 Pt77.3 Ni22.5 , and Ru0.9 Pt27.3 Ni71.8 colloidal nanocrystal clusters (CNCs) are obtained. In particular, the Ru0.3 Pt70.5 Ni29.2 CNCs exhibit excellent specific activities for formic acid and methanol electro-oxidation, that is, 14.2 and 15.3 times higher, respectively, than those of the Pt/C catalyst. Moreover, the Ru0.3 Pt70.5 Ni29.2 CNCs also possess better anti-CO-poisoning properties and diffusion ability than the other RuPtNi CNCs. The excellent formic acid and methanol electro-oxidation activities of RuPtNi CNCs are ascribed to the optimal ligand effects derived from the Pt, Ni, and atomic dispersed Ru atoms, which can improve the OH adsorption ability and further the anti-CO-poisoning capability. This research opens a new door for increasing the electro-oxidation properties of liquid fuels by using lower dosages of noble metals in Pt-based catalysts.

Thermally Responsive Photonic Fibers Consisting of Chained Nanoparticles

Fibers that can reversibly and passively change colors along with body temperatures are highly desired for potential applications including temperature sensors, smart wearables, and photonic devices. Here, we develop a facile strategy to fabricate thermochromic photonic fibers, which could exhibit tunable structural colors as a function of temperatures. The thermochromic fibers are prepared by aligning superparamagnetic, carbon-encapsulated Fe3O4 colloidal nanocrystal clusters (Fe3O4@C CNCs) in a thermoresponsive hydrogel, poly(N-isopropylacrylamide) (PNIPAM), forming chain-like structures under an external magnetic field before gelation. When the fiber is transferred from air to water at room temperature, it changes color from dark green to red as it swells. The red color can be reversibly changed back to green as the temperature is raised to 36 °C, while the fiber shrinks and the reflection peak shifts from 642 to 494 nm. The swelling of the fiber is anisotropic: by 60% in the diameter direction but 45% in the length direction. Therefore, the fiber can act as a thermochromic actuator.